Chromogenous tetrakis(aminophenyl) derivatives of benzodifuran



Aug. 15, 1967 E. J. GOSNELL 3,336,337

C HROMOGENOUS TETRAKISIAMINOPHENYL) DERIVATIVES OF BENZODIFURAN FiledAug. 51, 1961 BASE WEB, ORIGINAL TRANSFER COATING ON BACK CONTAININGTETRAKISIp-AMINOPHENYLI DERIVATIVE OF BENZODIFURAN la lfi ADHERENTCOATING ON FACE CONTAINING IZ; ELECTROPHILIC COLOR DEVELOPER BASE WEB,DuPucATEJ TRANSFER COATING ON BACKIOPTIONAQI INVENTOR. EARL J. GOSNELLATTORNEY United States Patent 3,336,337 CHROMOGENOUSTETRAKIS(AMINOPHENYL) DERIVATIVES 0F BENZODIFURAN Earl J. Gosnell,Irondequoit, N.Y., assignor to Burroughs Corporation, Detroit, Mich., acorporation of Michigan Filed Aug. 31, 1961, Ser. No. 135,359 7 Claims.(Cl. 260-343.4)

This invention pertains to chromogenous compounds which are relatedgenerally to the amino-substituted triphenylmethanes and which have theform of colorless, that is, white, or lightly colored solids, andapproach being colorless when in liquid solution, but which may beconverted to dark-colored forms as solids or in solution upon contactwith suitable color-developing substances. As applied to the printingand duplicating arts, marking in desired areas on base sheets may beaccomplished by effecting localized contact, in areas where imageelements are to be printed, between the chromogenous compound and thecolor-developing substance. Webs coated with films carrying individuallythe chromogenous compound and the color developer may be assembled in amanifolded set, so that localized pressure or impact will cause transferof material from a coating on the web surface of one manifolding unit toa coating on a contiguous web surface, where the desired localizedcontact is made to form the dark-colored materials in the image-markingareas.

Marking systems of these general types have been disclosed which utilizeknown chromogenous compounds. As examples of such chromogenous compoundsthere may be mentioned the leuco, or simple amino-substitutedtriphenylmethane, forms of malachite green, crystal violet, and ethylviolet; the corresponding amino-substituted triphenylmethyl carbinols;and the lactone forms, which are amino-substituted diphenylphthalides,corresponding to the above-mentioned leuco forms. These types ofchromogenous compounds have their peculiar properties with respect tostability of the colorless or leuco forms against spontaneous colordevelpment, and with respect to their reactions with variouscolor-developing agents having otherwise acceptable characteristics foruse as coatings on paper webs. The color-developing response may be tooeasily triggered in some cases and too sluggish in others, with somesubstances even requiring heating to develop a good dark mark. Thusproblems often arise from excessive background color in a coatingcontaining the chromogenous compound after periods of storage or longexposure to light or heat, from slow or insufl'icient production ofdark-colored materials upon contact with color-activating substances,and from limitations in the color hues and intensities of thedark-colored forms which can be developed from the chromogenoussubstances. To find the best answer to these problems for any givenapplication it is advantageous to have available a choice of additionaldifferent chromogenous substances.

Accordingly it is an object of the pressent invention to provide new andimproved, quite lightly colored substances having chromogenousproperties, which advantageously may be incorporated in a transferablecoating on a web surface to provide a novel manifolding unit, and whichare useful in carrying out improved methods of marking involving contactwith a color-activating material to develop dark-colored materials inareas where marking is desired.

It is another object of the invention to provide novel colorless orlightly colored compounds, having molecular structures convertible toquinonoid resonant forms, which ofier a new and improved variety ofchromogenous characteristics, and which develop, upon contact withcoloractivating materials, novel and much darker-colored substanceshaving generally desirable and useful color intensities and hues.

In accordance with the invention, there is provided a substance selectedfrom the group consisting of (A) a tetraaryl-substituted compound basedon the structural formula I'l II: in which, in each heterocyclic ring,the two hydrogen atoms attached to one of the carbon atoms in the ringare replaced by a pair of p-aminophenyl aryl radicals having bonds tothat carbon atom; (B) a diepoXy-substituted compound, having thestructure of a tetraaryl-substituted compound A, in which the twop-aminophenyl radicals in each of the pairs of such radicals are linkedby an epoxy bridge between respective positions in those radicals orthoto the positions of the aforementioned bonds (C) a dioxo-substitutedcompound, having the structure of a compound B, in which, in each of thefirstmentioned heterocyclic rings, the remaining carbon atom Willi twohydrogen atoms is oxo-substituted; and (D) N- substituted derivatives ofeach of such compounds A, B, and C in which each individualN-substituent is selected from the group consisting of an alkyl radicalof not more than four carbon atoms, the benzyl radical, and the phenylradical.

In accordance with a feature of the invention, a new composition ofmatter comprises the dark-colored substance developed by contact of acolorless or lightly colored chromogenous compound selected from thegroup identified above, such compound having two heterocyclic rings eachcontaining a carbon atom bonded to a hetero oxygen atom wherein thatcarbon atom is the methane carbon atom of a bis(p-aminophenyl)methanegroup, with an electrophilic color-activating substance for opening thebonds from such methane carbon atoms to the respective hetero oxygenatoms to permit quinonoid resonance in the bis-(p-aminophenyl)methanegroups and convert the chromogenous compound to the dark-coloredsubstance.

In a manifolding unit comprising a base web having on one side a coatingmade up of a film-forming material containing a colorless or lightlycolored chromogenous compound transferable upon impact from the coatingto a surface contiguous therewith, the improvement is provided, inaccordance with the invention, in which the chromogenous compound isselected from the group consisting of the compounds identified as A, B,C, and D hereinabove, this manifolding unit being adapted, upon suchimpact and transfer of the chromogenous compound to the contiguoussurface, to produce a dark-colored material by the action of anelectrophilic color-activating material on the contiguous surface inopening the bond in each of the heterocyclic rings from the carbon atomscarrying the pair of p-aminophenyl aryl radicals to the adjoining heterooxygen atoms, permitting quinonoid resonance in the groups comprisingthe pairs of aryl radicals and the carbon atoms carrying them.

In a related feature of the invention, a manifolded set comprises afirst base web having on one side a transfer coating made up of afilm-forming material which is rupturable upon impact and which containsas a finely dispersed phase numerous minute droplets, or cells, of aliquid carrying, dissolved therein, a colorless or lightly coloredchromogenous compound selected from the aforementioned group, andfurther comprises a second base web having on one side an adherentcoating containing an electrophilic color-activating material, thesefirst and second base webs being maintained disposed together in face toface relationship with their respective transfer and adherent coatingsin contiguity with each other, whereby, upon local rupture of thetransfer coating and release of the liquid vehicle, contact is effectedof the chromoge-nous compound in the vehicle with the electrophiliccolor-activating material in the adherent coating, causing the bond ineach of the heterocyclic rings from the carbon atom carrying the pair ofp-aminophenyl aryl radicals to the adjoining hetero oxygen atom to openand convert the chromogenous compound locally to a dark-coloredmaterial.

In accordance with a method feature of the invention, the method ofmarking by developing dark-colored materials from colorless or lightlycolored chromogenous compounds comprises providing a chromogenouscompound selected from the aforementioned group of compounds each ofwhich includes in each heterocyclic ring a carbon atom, carrying a pairof aryl radicals, having a bond to an adjoining hetero oxygen atom, andbringing the chromogenous compound into contact, in areas Where markingis desired, with an electrophilic color-activating substance for openingthat bond in each heterocyclic ring to permit quinonoid resonance andproduce a dark-colored form of the chromogenous compound by the actionthereon in such areas of the electrophilic substance.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawing, and itsscope will be pointed out in the appended claims.

The single figure of the drawing shows in exploded view two manifoldingunits, suitable for use together in face to face contiguity, with orwithout additional similar manifolding units, in a manifolded set. Themanifolding units are illustrated in cross-section with the thicknessesof the base webs and of the coatings on the web surfaces greatlyexaggerated for convenience of illustration.

A manifolding unit embodying the present invention is shown in the upperportion of the exploded view of the drawing. In such a manifolding unit,comprising a base web 11 having on one side, usually on the backsurface, a coating 12 made up of a film-forming material containing acolorless or lightly colored chromogenous compound transferable uponimpact from the coating to a surface contiguous therewith such as thesurface on the face of another base web 13, the present invention isembodied in an improvement in which the chromogenous compound is one ofthe novel substances provided by the invention.

The chromogenous compounds involved in the aforementioned embodiments ofthe present invention may be considered to be based on compounds havingthe structural formula 4 and the isomeric structural formula 0- I'I) HgAs will appear from the specific names for these isomeric compounds,they (and also their derivatives having epoxy bridges, and otherderivatives having additionally, oxo substituents forming lactone rings)may be viewed as tetrakis(p-aminophenyl) derivatives of benzodifuran.These isomeric compounds may be named respectively 1,l,5,5,- tetrakis(paminophenyl) 7 hydro 1H,3H benzo(l, 2-c:4,5-c)difuran and1,1,7,7-tetrakis(p-arninophenyl)-5-hydro-lH,3H-benzo(l,2-c:4,5-c)difuran. Each of these two compounds hastwo heterocyclic furan rings fused to the central benzene nucleus, andeach of these furan rings includes one carbon atom carrying twounsubstituted hydrogen atoms, as may be seen at the bottom of the laststructural formula shownabove.

The last mentioned carbon atoms may be oxo substituted; that is, the twohydrogen atoms carried by each carbon atom may be replaced by an oxygenatom. Each furan ring thus assumes a gamma-lactone structure, instead ofthe cyclic ether structure, giving a bifunctional lactone, or dilactone,compound. The respective dilactone compounds may be named 3,3,7,7tetrakis(p aminohenyl)-lH,3H-benzo( l,2-c:4,5-c')difuran-l,5(7H)-dioneand 3,3,5,5-tetrakis(p-arninophenyl)-lH,3H benzo(1,2-0:4,5-c)difuran-l,7(5H)-dione.

Dilacetone compounds of the last-mentioned type are disclosed andclaimed in the concurrently filed application for Letters Patent of theUnited States Ser. No. 135,264, now matured to US. 3,268,537, entitledChromogenous Aminophenyl Derivatives of Benzodifurandione and MarkingMethod Using Same," filed in the names of Earl I. Gosnell and John F.McCarthy, Jr., and assigned to the same assignee as the presentinvention. A representative N-substituted dilactone compound may besynthesized by dissolving one mole of N,N-dimethylaniline in about fourtimes its weight of carbon disulfide and stirring in about 0.9 mole ofanhydrous aluminum chloride as a catalyst. After dissolution of the AlCl0.2 mole of pyromellitic dianhydride is added, stirred, and allowed tostand. The upper layer of the CS is decanted and 1250 ml. of 8% sulfuricacid added to it slowly. After dilution with about 10 liters of waterand standing, the first stage of the synthesis gives and approximatelyyield of a solid intermediate product which is a mixture of two isomericcompounds having the structural formulas where each radical designated Xis the p-dimethylaminophenyl radical derived from theN,N-dimethylaniline. In the second stage of the synthesis, a portion ofthe isomeric intermediate mixture then is heated at reflux temperaturefor 24 hours, with a further amount of N,N-dimethylaniline equal toabout 4.5 to 5 times the equimolar weight, in a volume of liquid aceticanhydride weighing about 7 to 8 times as much as the weight of the Nsubstituted aniline. Cooling and filtering gives a solid aceticanhydride-insoluble product of light yellow color, and pouring thefiltrate over crushed ice and filtering gives a solid aceticanhydride-soluble product of light greenish yellow color, both in goodyields. A mixture of these two solid products may be obtained byflushing with ice water before filtering out the aceticanhydride-insoluble fraction.

These two light-colored products are the chromogeneous substancesselected from the group consisting of the isomeric compounds having thestructural formulas where X is as above and the radical designated Xalso is the p-dimethylaminophenyl radical, derived in this instance fromthe dimethylaniline used in the reaction with the intermediate mixture.It will be appreciated that aniline itself, or other N-substitutedanilines, may be used in forming the intermediate mixture withcorresponding variations in the p-aminophenyl radical X, while aniline,or still another N-substituted aniline, may be used as the reagent withthe intermediate isomers to get the dilactone product with othercorresponding variations in the paminophenyl radical X. Yields of theacetic anhydride-insoluble and -soluble fraction vary, and standardpurification procedures such as solvent or freeze crystallizations andselective solvent extractions can be utilized where necessary to recovercrystalline products having substantially colorless creamy or lightpastel shades. The dilactones generally can be heated well above 300 C.with out melting or decomposition.

The synthesis of a specific chromogenous dilactone compound, or isomericmixture of such compounds, having the structure represented by theformulas given above where all of the radicals designated both X and Xare pdimethylaminophenyl groups, is mentioned hereinabove by way ofexample. The two isomeric fractions have very low solubilities in mostof the common organic solvents. However, they dissolve up to a fewpercent or more in some of the solvent vehicles such as the simple orchlorinated phenyl ethers and chlorinated polyphenyls, and the solutionof either one or both of the above-mentioned fractions gives a darkblue-green colored form when brought into contact with an electrophilicdeveloper substance. The aforementioned application of Earl J. Gosnelland John P. McCarthy, Jr., is referred to for further details regardingthe synthesis and properties of numerous dilactone compounds.

A variety of such dilactone compounds, themselves useful as chromogenouscompounds as well as in making the benzodifuran derivatives of interestin accordance with the present invention, may be synthesized. Thus, theuse of unsubstituted aniline in the synthesis described above gives thetetrakis(p-aminophenyl)benzodifurandione or dilactone substance withoutN-substituents, X and X both being p-aminophenyl radicals, and contactwith developers, as pointed out yields a reddish or purplish tan coloredform. It is much preferred, however, to use substituted anilines,particularly N,N-disubstituted anilines. Thus the N,N-dimethylanilineadvantageously is used in many cases to make the intermediate producthaving the pdimethylaminophenyl group for the radical X. However,appropriate variations in the substituted aniline reacted with theintermediate product in the second stage of the synthesis describedabove yield dilactone products in which the radical X consists ofdifferent N-substituted p-aminophenyl groups, preferably otherN-dialkyl-substituted groups with alkyl radicals of not over threecarbon atoms. X accordingly may be the p-diisopropylaminophenyl radical,while X remains the p-dimethylaminophenyl radical. As pointed outparticularly in the aforementioned Gosnell and McCarthy application,this dilactone substance also gives a dark blue-green quinonoid form oncontact with a developer material. Alternatively the compound mayinclude butylamino groups. Blue-green forms also may be obtained fromthe dilactone in which X is the p-N-benzyl-N-ethylaminophenyl group,while the dilactone in which X is the p-dibenzylaminophenyl group givesa bluish green to green dark-colored form. X may be thep-N-methylanilinophenyl group with N-phenyl and N- methyl substitutents,from which a dark green form may be developed. As mentioned hereinbelow,there may be halo or methyl substituents on the phenyl ring in thepaminophenyl radical. Thus, when m-chloro-N,N-diethylaniline is used inthe second stage of the synthesis, the resulting dilactone product has-o-chloro-p-diethylamin0- phenyl groups for the X radicals, X stillremaining the p-dimethylaminophenyl group. This substance gives a greendark-colored form. When X is the p-diethylaminoo-tolyl group, thequinonoid form has a strong dark green color. Thus certain compounds,with halo and methyl substituents in the ortho, and meta, positions ofthe p-aminophenyl groups, are equivalent to the compounds without suchsubstituents.

A preferred dilactone substance of the type just described, havingdialkylaminophenyl groups, will be seen to include a colorless orlightly colored chromogenous compound based on the structure ofpyromellitic diahydride O O 0 0 C C U 0 including, fused to oppositesides of the benzene nucleus,

two heterocyclic rings 0o 00 0 each containing a hetero oxygen atom inthe ring, and to each of which two other oxygen atoms are attached. Oneof these two oxygen atoms attached to each heterocyclic ring thereof isreplaced by two p-dialkylaminophenyl groups, in which each individualone of the four alkyl radicals has not more than three carbon atoms.

Instead of a dilactone substance, there may be used the correspondingbifunctional cyclic ethers, which are the usually N-substitutedderivatives of the 1,l,5,5-tetrakis(p-aminophenyl) -7hydro-lH,3H-benzo(l,2-c:4,5-c) difuran and of its isomer, shown above.To produce the bifunctional cyclic ethers, or dicyclic ethers,appropriate dilactones, such as those just mentioned, may be added toethyl ether which is maintained at reflux temperature and which containsaluminum lithium hydride, and the bifunctional cyclic ether recovered byfiltration and solvent evaporation. These products after purificationhave chromogenous characteristics similar to those of the correspondingdilactone materials, having the same N-substituted p-aminophenyl groupsrepresented by the radicals X and X in the structural formulas shownabove. The present invention is directed particularly to these productsand to certain epoxy-substituted compounds related thereto.

As an example of preparation of the bifunctional cyclic ethers of thepresent invention, either isomer, or a mixture of the two isomers, ofthe dilactone substance having the isomeric formulas given above, inwhich all four of the radicals designated X and X arep-dimethylaminophenyl radicals, may be used as the starting material.Sixteen grams of the AlLiH are mixed into 550 ml. of ethyl ether,previously rendered anhydrous by drying over metallic sodium, and themixture is refluxed with stirring for 1 hour to effect partial solutionof the hydride. For 15 minutes thereafter 13.3 grams (0.02 mole) of thedilactone substance are added a portion at a time, followed by 2 morehours of refluxing to allow the reaction to proceed. After cooling,about 25 ml. of water are added slowly with stirring so that unwantedreagent may be separated in granular form. The bifunctional cyclic etherwhich is recovered thereafter is a tetraaryl-substituted compound basedon the structural formula in which, in each hetcrocyclic ring, the twohydrogen atoms attached to one of the carbon atoms are replaced by apair of N-substituted p-aminophenyl aryl radicals, specificallyp-dimethylaminophenyl radicals. A blue-green colored form may beproduced by eifecting contact with a developer substance such asattapulgite or magnesium trisilicate. It will be appreciated from thediscussion of the dilactone starting substances that N-substitutedderivatives of the bifunctional cyclic ether compound are useful inwhich each individual N-substituent is selected from the groupconsisting of an alkyl radical of not more than four carbon atoms, thebenzyl radical, and the phenyl radical.

In the structural formula just given, both p-aminophenyl aryl radicalsin the pair attached to one of the carbon atoms in each heterocycliering have bonds to such respective carbon atoms. The present inventionalso is embodied by a diepoxy-substituted compound, having the structureof the tetraaryl-substitutedthat is,tetrakis-(p-aminophenyl)-substitutedcompound as in the structuralformula just given, but, in which the two p-aminophenyl radicals, ineach of such pairs of aryl radicals are linked by an epoxy bridgebetween respective positions in the radicals ortho to the carbon atom inthe heterocyclic ring. These compounds may be called rhodamine dicyclicethers. Another embodiment is a dioxo-substituted compound, having thestructure of the diepoxy-substituted compound just described, but inwhich, in each of the heterocyclic rings, the remaining carbon atomcarrying two hydrogen atoms is oxo-substituted. The diepoxy-substitutedcompound (and its N-substituted derivatives or rhodamine cyclic ethers)conveniently are obtained by reduction of the corresponding compoundhaving both diepoxy and dioxo substituents, which may be called arhodamine dilactone. The latter compound may be represented by theisomeric structural formulas and O/C /C\0 for 4 to 5 hours at C. whilestirring the melt continuously. There is formed in the melt at moderateyield of a bifunctional compound including the structure It will be seenthat the portion of the molecular structure illustrated here is thelactone of Rhodamine B, that is 3- 6-bis(diethylamino)fiuoran. It willbe understood further that each molecule of pyromellitic dianhydridelikewise acquires a similar Spiro-linked xanthene structure, notillustrated here, on the other side of the benzene nucleus, whereanother one of the diahydride carbonyl oxygen atoms is replaced with twomore aminophenyl radicals. Thus a third molecule of water is split off,formed from this oxygen atom and the hydrogen atoms in the 6-positionson two additional 3-diethylaminophenol molecules. A second xantheneepoxy bridge also is formed by removal of a fourth water molecule fromthe two adjacent phenolic hydroxyl groups in these two additionalaminophenol molecules. Two isomers may be formed in this way, and bothusually are in some amount, depending on which of the two carbonyloxygen atoms is replaced, as just described, on the other side of thebenzene nucleus of a given pyromellitic dianhydride molecule.

To recover this product from the reaction mixture, however, the meltconveniently is cooled, finely powdered, and digested with diluteaqueous ammonium hydroxide, obtained from 40 grams of 28% NH OH in 0.8liter of additional water, for several hours at room temperature,leaving undissolved the isomeric bifunctional carbinols This substanceis separated by filtering it out of the ammonium hydroxide solution,washing with fresh dilute amomnium hydroxide, and drying. Reclosure ofthe two lactone rings in each molecule is accomplished by refluxing thecarbinol with benzene, which conveniently is done with a standardcondenser and Stark and Dean tube apparatus to remove the water splitoff from the carbinol hydroxyl groups and the adjacent carboxyl hydrogenatoms. The resulting benzene solution is then filtered and evaporatedunder vacuum to recover the bifunctional rhodamine lactone substance,whose structure is illustrated by the isomeric formulas'shown above, allthe amino hydrogen atoms being replaced by ethyl radicals in thisexample.

This product is more or less colorless, having a creamy to light pinkcolor. By using other N-substituted mor 3-aminophenols, a variety ofother chromogenous rhodamine dilactone compounds, having differentN-substituents and also only lightly colored, may be prepared, as willbe understood from a consideration of the various N-substituteddilactone compounds discussed hereinabove, which are the correspondingbifunctional lactones without the epoxy bridges. The colored forms ofthese rhodamine dilactone substances resemble in hue the colored formsof the corresponding rhodamine lactones, giving generally bluish redcolors. However, the rhodamine dilactone substances share with themonofunctional rhodarnine lactone compounds a tendency toward prematureopening of the lactone rings, which may cause coloration of thechromogenous material before marking contact has been effected with thedesired color-activating material. Of course, the rhodamine dilactonesubstance may be protected from premature contact with atmospheric orother environments which permit premature coloring.

However, it may be preferable to convert the rhodamine dilactones to thecorresponding bitunctional cyclic ether substances, which haveconsiderably more stability against adventitious color formation as whenexposed to a humid atmosphere. Such bifunctioual cyclic ether substancesinclude the structure with suitable N-substituents. Each monotunctionalmolecular arrangement in this category of bifunctional substances willbe seen to include the structure of 3',6'-diaminospiro(phthalan-l,9'-xanthene), as illustrated here. Thesebifunctional cyclic ether substances likewise may have either, or amixture of both, of the isomeric forms corresponding to the two isomericstructural formulas given above for the rhodamine dilactone substances.Any two isomeric compounds of this structure give very similar coloredforms, which also are similar in hue to the colored forms produced fromthe corresponding rhodamine dilactone and rhodamine lactone substances,although with some N-substituents minor differences in hue may beobserved, even between isomeric pairs, depending on the color-activatingsubstances used.

All of the bifunctional substances in the categories of bifunctionallactones, cyclic ethers, rhodamine lactones, and rhodamine cyclic ethershave high melting points and generally can be heated above 300 C. in aneutral atmosphere without melting or decomposing. Several nonpolar ormildly polar solvents may have to be tried in order to find one whichwill dissolve several percent or more of these bifunctional chromogenoussubstances.

The bifunctional rhodamine cyclic ethers, having the functionalarrangement illustrated above, are obtained by reduction of thecorresponding chromogenous rhodamine dilactone substances, using eitherof the isomeric forms thereof or a mixture of such forms. Ten grams ofthe rhodamine dilactone, synthesized and recovered as described above,are stirred slowly into a semidissolvcd mixture of 12 grams of aluminumlithium hydride in 0.4 liter of anhydrous ethyl ether. The resultingmixture is refluxed for two hours, to permit reaction, cooled, and wateris added dropwise. The ether layer is decanted, dried with a soliddesiccant such as anhydrous sodium sulfate, and the ether evaporated toobtain the chromogenous, substantially colorless or light pink, solidrhodamine dicyclic ether substance. Upon intimate contact with adeveloper substance such as attapulgite or magnesium trisilicate, thisproduct is converted to an intense, bluish red, colored form.

In the preferred chromogenous compounds of the present invention. theamino nitrogen atoms carry substituents, for which the methyl and ethylN-substituents are chosen frequently. Propyl and isopropylN-substituents also function similarly, and chromogenous compounds withp-dialkylaminophenyl groups in which each individual alkyl radical hasnot over three carbon atoms are recommended. In these bifunctionalcompounds all four of the aminophenyl groups preferably aredisubstituted as here recommended. Also, and more generally, butylsubstituents in place of one or both of the amino hydrogen atoms providequite similar properties, so that alkyl radicals of not more than fourcarbon atoms are suitable. Examples of N-benzyl and N-phenyl groups alsoappear hereinabove.

Equivalent results also may be obtained, for example, with certainsaturated monoalkyl radicals having five carbon atoms or with themono-n-hexyl radical as N-substituents, and N-substituted cycloalkylgroups such as the cyclopropyl and cyclohexyl groups may be present, butthese N-substituents are not preferred. As further examples, theN-phenyl-substituted compounds may be modified by including naphthylradicals instead of phenyl radicals as N-substituents, or certain smalladditional substituents may be included on the N-substituted radicalsmentioned above, and generally equivalent properties still will beobtained; in this connection such N-substitutcd groups as theehloromethyl, hydroxyalkyl (e.g., betahydroxyethyl, gamma-hydroxypropyl,or delta-hydroxybutyl), sulfophenyl, tolyl, or one of the methylbenzylradicals may be mentioned. Equivalent to the aminophenyl groupsthemselves in some chromogenous compounds are amino-l-naphthyl groups;thus 4-diethylaminol-naphthyl groups may replace p-diethylaminophenylgroups. Instead of N-substituted amino groups, equivalent results alsomay be expected with piperidino groups, or an entire N-substitutedp-aminophenyl group may be replaced by the 9-julolidyl radical It willbe appreciated likewise that substantially equivalent properties alsoare obtainable in the chromogenous compounds when one small substituentor several small substituents, notably one or more methyl, chloro,bromo, fluoro, or nitro radicals, is or are substituted for one or moreof the available hydrogen atoms on the phenyl rings in the aminophenylradicals or one the benzene nucleus one side of which is in theheterocyclic ring. Typical exsamples of such substituents in theaminophenyl radicals are discussed in the aforementioned Gosnell and Mc-Carthy application, where it is disclosed in general, for theaminophenyl radicals in which the amino substituent is taken to be inthe 4-position, that the phenyl ring may ;carry at least one substituentdefined as being selected from the group consisting of any single one ofthe methyl, fluoro, chloro, and bromo substituents in the 2-position,any single one of these substituents in the position (or 3-position),and both of these single substituents individually in the 2- andS-positions. Conversion of dilactone compounds having such substituentsto the corresponding bifunctional cyclic ether compounds, for example,produces useful chromogenous substances equivalent in nature andfunction to the compounds without such substituents.

Referring again to the manifolding unit comprising the base web 11having the back coating 12, it is possible to incorporate one of thegenerally light-colored chromogenous compounds, as identified above, inthe solid state in a back coating of waxy or thermoplastic filmformingmaterial, which may be transferred from the base web upon impact todeposit some of the chromogenous material on a surface carrying acolor-activating material. Production of the darker-colored form occursbest, however, if the chromogenous substance is dissolved in a solvent,permitting intimate contact of the molecules of the chromogenoussubstances with the color-developing material. It is possible to providesome of this solvent on the surface carrying the color-developingmaterial. Preferably, however, the film-forming material of the backcoating 12, which is rupturable upon impact or other localized pressure,contains as a finely dispersed phase numerous cells of a liquid vehiclecarrying the colorless or lightly colored chromogenous compound. An oilysolvent vehicle advantageously is used, such as chlorinated biphenyl,benzyl butyl phthalate, benzyl salicylate, phenyl ether or halogenatedphenyl ethers, or mixtures of such vehicles. A solution by weight orfrom about 0.5% to 5%, or even is solubility permits, of thechromogenous compound in such a solvent vehicle may be prepared, forexample, and then emulsified in a conventional aqueous film-formingmaterial such as polyvinyl alcohol in colloidal solution, or such as acolloidal aqueous solution of casein, gelatin, or the like. Theresulting emulsion is coated on the back surface of the base web 11,which may be a strip or sheet made of paper or other fibrous material orof a plastic film base, and then is dried to form the coating 12containing numerous liquid cells of the water-insoluble solvent vehiclecarrying, dissolved therein, the chromogenous substance, these liquidcells being finely dispersed throughout the solid dried film ofhydrophilic material which makes up the continuous phase in the coating12. The dried coating 12 may be about 0.001 inch thick, and becomesinsolubilized during the drying.

The manifolding units of the invention, carrying the novel chromogenouscompounds, are adapted and arranged to produce a dark-colored materialupon local impact and rupture of the coating 12 and contact of thechromogenous compound in the liquid vehicle with a contiguous surfacecarrying a color-activating material, which advantageously may be aninorganic electron acceptor material. Solid particles of the lattermaterial conveniently are dispersed in water, mixed with an aqueouspaper-coating starch solution in the proportions of roughly five partsby weight of the inorganic material to one part of starch on a drybasis, coated on the face of the base web 13 of paper or the like, anddried to form a dry, adherent coating 14, roughly 0.0005 inch thick,containing the color-activating material. Alternatively an aqueous latexof polybutadiene-styrene plastic material may replace some or all of thestarch as the film-forming material. Thus the coated web 13, shown inthe lower portion of the exploded view of the drawing, forms a secondmanifolding unit for use with the upper manifolding unit provided by thecoated web 1 1.

For use as a manifold set, the first and second. base Webs 11 and 13 aremaintained disposed together in face to face relationship, as suggestedby the bracket at the left of the drawing, with the transfer coating 12on the back of sheet 11, containing one of the chromogenoustetraaryl-substituted benzodifuran substances of the type describedhereinabove, held in contiguity with the adherent coating 14 on the faceof the sheet 13, containing the inorganic electron acceptor material.For producing simultaneously an original and one copy sheet by use of atypewriter, for example, or by direct writing with pen or pencil, theweb 11 advantageously serves as the original and the face-coated web 13serves as the duplicate. These manifolding units may be fastenedtogether in a pad, or simply laid one over the other on a writingsurface, or held together on the platen of a typewriter.

Typing or Writing impact, or other printing pressure on the face of thesheet 11 causes localized rupture of the back coating 12. This releasesthe vehicle, carrying the colorless or lightly colored chromogenousmaterial, from those ones of the tiny cells in the coating 12 whichoccupy the areas immediately beneath the areas of impact on the originalprinting or writing surface. Thus the chromogenous material in solution,upon such marking impact, is transferred to the surface having thecoating 14. This coating, made as previously described, permits adequateabsorptive contact of the chromogenous material, so transferred in theimage areas to be duplicated, with the many small particles of theinorganic electron acceptor material in those areas of the coating 14.Where this contact is effected, the dark-colored material is produced ordeveloped locally by the action of the inorganic electron acceptorsubstance on the chromogenous compound, thus forming the duplicate imageon the face of the duplicate sheet 13.

It will be understood that, if desired, a coating 15 may be formed onthe back surface of the duplicate Web 13 in just the same manner as theback coating is formed on the original web 11. With this optional backcoating 15 on the web 13, one or more additional duplicate coated webs,identical with the coated Web 13, may be manifoided beneath the web 13,permitting simultaneous production of triplicate and quadruplicatecopies. In fact, most of the electron acceptor materials, when appliedin face coatings such as the coating 14 described above, themselvesprovide good original printing or writing surfaces, so that a sheet suchas the sheet 13, when provided with the back coating 15 as well as theface coating 14, may serve either as an original sheet or as a duplicatesheet in a manifolded set or stack. Thus identical paper sheets, eachhaving white or light-colored face and back coatings acceptable asordinary paper surfaces to most users, may be manifolded in sets of twoor more, or several sheets may be manifolded in which the face coatingmay be omitted from the top sheet only and the back coating may beomitted from the bottom sheet only. No smudging or soiling of the papersheets or of the users hands occurs in ordinary usage, and dark-coloredmaterial is formed only in the duplicate image areas by theaforementioned action of the developer material on the almost colorlessor white, or rather lightly colored, chromogenous material.

Numerous inorganic electron acceptor materials are available forincorporation as small solid particles in the face coating 14. Thesematerials include certain clays, siliceous materials, and otherinorganic materials such as attapulgite and argosite clay, silicates ofmagnesium, calcium, and aluminum such as magnesium trisilicate, which isa precipitated hydrated silicate having the approximate formula Mg Si O-5H O, calcined diatomaceous silica, activated silica, sodium aluminumzeolite material and related silicate zeolite materials in which sodiumis replaced by the cations of potassium or other metals having similarfunctions, attapulgite with similar cation replacements, pyrophyllite,bentonite, halloysite, magnesium montmorillonite, calcium sulfate, zincsulfate, barium sulfate, basic aluminum sulfate (aluminum hydrate), andcalcium fluoride.

In more general terms, the manifolding unit including the coating 12 isadapted to produce a dark-colored material upon local impact andtransfer of the chromogenous compound to the contiguous surface of theweb 13 and contact of that compound with an electrophiliccoloractivating material, carried by that contiguous surface in acoating generally similar to the above-described face coating 14 on theweb 13. Referring to the structural formulas shown hereinabove for thesubstituted benzodifuran chromogenous compounds, each compound has twoheterocyclic ring components CX -OCH or fused to the central benzenering, where X represents the pair of aryl radicals, more specificallythe bis(paminophenyl) or spiro-linked xanthenyl substituent, havingbonds to one of the carbon atoms in the ring, such carbon atom in turnhaving a bond to the adjoining hetero oxygen atom as shown in the ringcomponents just illustrated. An electrophilic material such as a sourceof protons, preferably a weakly acid proton source, or an aprotic acid(a Lewis acid), serves upon contact as a color-activating or developingmaterial for opening the bond in each of the heterocyclic rings from thecarbon atom carrying the pair of aryl radicals X to the adjoining heterooxygen atom, permitting quinonoid resonance in the groups comprisingthese pairs of p-aminophenyl aryl radicals and the carbon atom carryingeach pair. The latter carbon atoms resemble the methane carbon atoms ofthe p-amino-substituted diphenylmethane and triphenylmethane dyecompounds. The cleavage of the heterocyclic rings in the chromogenouscompound is understood to convert the compound locally at the point ofcontact to a quinonoid resonant form having the desired in tense darkcolor, although the precise structure of the dark-colored formsapparently cannot be established incontrovertibly by reasonably usablemethods and is not a part of the present invention.

It will be appreciated that the choice of a color-activating materialfor use with a particular chromogenous substance in a specific systemmay require the exercise of the good judgment of one experienced in theart, and in some instances a little experimentation, to arrive at areasonably effective combination of materials. The same chromogenoussubstance can produce dark-colored forms having noticeably differentcolor responses or hues when brought into contact with differentelectrophilic materials, and the color intensity of the colored formsproduced in a given system or arrangement can show gross variations whendifferent color-activating materials are used. Similar bifunctionalchromogenous substances may show minor variations in color response,probably due to production or separation of isomers in differentproportions. While the chromogenous substances of the present inventionproduce dark-colored forms of useful intensities after being broughtinto ordinary contact with many electrophilic color-activatingmaterials, the use of certain color-activating materials may require theapplication of heat, or utilization of other means of obtaining moreintimate or effective contact of the materials, to cause reasonably goodcolor development. This might be accomplished, for example, byconcentrated infrared irradiation or by conductive contact with a hotsurface. It has been found highly desirable, furthermore, to try anumber of solvent liquids for a given chromogenous compound, when it isto be brought into contact with a given color-activating substance, toobtain the concentration and other environmental conditions which favorthe eflicient formation of a dark-colored material with desirable colorintensity and hue.

It will appear from the above that marking or printing may beaccomplished, without the use of conventional inks containing dyes andpigments, by using instead of such inks an oily ink vehicle in which achromogenous compound of the invention is dissolved. For letterpressprinting the resulting oily vehicle is applied to the type, which thenis impressed on a web surface having a coating such as theaforementioned face coating 14 containing an electrophiliccolor-activating substance. Alternatively sheets having such a facecoating may be used in a typewriter provided with a ribbon impregnatedwith an oily ribbon-inking vehicle containing the chromogenous substancein solution. A ribbon so impregnated will not soil the fingers orclothing while being installed on or removed from the typewriter.

Such arrangements involve embodiments of the method, in accordance withthe invention, of marking by developing dark-colored materials fromcolorless or lightly colored chromogenous compounds. This methodaccordingly comprises providing a chromogenous substance selected fromthe group of benzodifuran based tetrakis(p-aminophenyl) derivativesdescribed hereinabove, and bringing this chromogenous substance, whichpreferably is dissolved in an oily vehicle, into contact, in areas wheremarking is desired, with the electrophilic color-activating substance,which may be a weak acid such as citric acid powder or tartaric acid. Asdescribed above, this contact opens the bond in each of the heterocyclicrings from the carbon atom carrying the pair of aryl radicals to theadjoining hetero oxygen atom aud produced a dark-colored form in theareas of contact by the action of the electrophilic substance on thechromogenous substance. In another embodiment of this method, the solidcolorless or lightly colored chromogenous compound is incorporated in asurface coating and brought into contact with an electrophilic substanceby applying such substance, in the form of liquid droplets of aceticacid, to the surface coating where dark-colored marks are desired. Themethod, of course, may be carried out also by the use of the manifoldedset shown in the drawing. To complete an illustration of such a methodembodying the invention, the back coating 12 on the web 11advantageously contains minute droplets or cells (which may or may notbe encapsulated in thin shells of a substance differing from that of thecontinuous phase of the coating) of an oily liquid in which is dissolvedone of the chromogenous compounds. Thus a chromogenous compound isprovided which, under marking, printing, or writing impact or pressureapplied directly or indirectly to the face of the web 11, is forced fromthe cells in the coating 12 and brought into contact, in localized areason the face coating 14 carried by the duplicate web 13, with aninorganic electron acceptor substance in the coating 14 to develop adark-colored material, in the areas of the marks to be duplicated, bythe action of such substance on the chromogenous compound.

Accordingly, it appears that the present invention provides a group ofnovel substances offering a new and desirable choice of chromogenouscharacteristics useful, by way of example as illustrated hereinabove, inmarking and duplicating systems.

While there have been described what at present are considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention. It is aimed, therefor, inthe appended claims to cover all such changes and modifications whichfall within the true spirit and scope of the invention.

What is claimed is:

1. A chromogenous compound selected from the group consisting of (A) atetraaryl-substituted compound based on the structural formula in which,in each heterocyelic ring, the two hydogen atoms attached to one of thecarbon atoms are replaced by a pair of aryl radicals having bonds tosaid carbon atoms, said aryl radicals being selected from the groupconsisting of (i) the paminophenyl radical, (ii) p-aminophenyl radicalshaving on the phenyl ring a substituent selected from the groupconsisting of methyl, chloro, bromo, fiuoro and nitro radicals, (iii)the amino-l-naphthyl radical, and (iv) the 9-julolidyl radical; (B) adiepoxy-substituted compound, having the structure of atetraaryl-substituted compound A, in which the two p-aminophenylradicals in each of said pairs are linked by an epoxy bridge betweenrespective positions in said radicals ortho to the positions of saidbonds; (C) a dioxo-substituted compound, having the structure of acompound B, in which, in each of said first-mentioned heterocyclicrings, the remaining carbon atom with two hydrogen atoms isoxosubstituted; and (D) N-substituted and N, N-disubstituted derivativesof compounds A, B, and C in which each individual N-substituent is aradical selected from the group consisting of (i) an alkyl radicalselected from the group consisting of methyl, ethyl, propyl, and butylradicals, (ii) benzyl, (iii) methylbenzyl, (iv) phenyl, (v) naphthyl,(vi) chloromethyl, (vii) beta-hydroxyethyl, (viii) gamma-hydroxypropyl,(ix) delta-hydroxybutyl, (x) sulfophenyl, and (xi) tolyl.

2. A tetraaryl-substituted compound based on the structural formula inwhich, in each heterocyclic ring, the two hydrogen atoms attached to oneof the carbon atoms are replaced by a pair of p-aminophenyl radicals,each of said four p-aminophenyl radicals having at least oneN-substituent selected individually from the group consisting of (i) analkyl radical selected from the group consisting of methyl, ethyl,propyl, and butyl radicals, (ii) benzyl, (iii) methylbenzyl, (iv)phenyl, (v) naphthyl, (vi) chloromethyl, (vii) beta-hydroxyethyl, (viii)gamma-hydroxypropyl, (ix) delta-hydroxybutyl, (x) sulfophenyl, and (xi)tolyl.

3. A tetraaryl-substituted compound based on the strucmethyl, ethyl,propyl and butyl radicals.

4. A compound based on the structural formula H1 H2 /o\ 0 o C o H, H, inwhich, in each heterocyclic ring, the two hydrogen atoms attached to oneof the carbon atoms are replaced by a pair of p-aminophenyl radicalshaving bonds to said carbon atom, the two p-aminophenyl radicals in eachof said pairs being linked by an epoxy bridge between respectivepositions in said radicals ortho to the positions of said bonds, andeach of said four p-aminophenyl radicals having at least oneN-substituent selected individually from the group consisting of (i) analkyl radical selected from the group consisting of methyl, ethyl,propyl, and

butyl radicals, (ii) benzyl, (iii) methylbenzyl, (iv) phenyl,

16 (v) naphthyl, (vi) chloromethyl, (vii) bet a-hydroxyethyl, (viii)gamma-hydroxypropyl, (ix) delta-hydroxybutyl, (x) sulfophenyl, and (xi)tolyl.

5. A compound based on the structural formula bonds.

6. A compound based on the structural formula in which, in eachheterocyclic ring, the two hydrogen atoms attached to one of the carbonatoms are replaced by a pair of p-aminophenyl radicals having bonds tosaid carbon atom, the two p-aminophenyl radicals in each of said pairsbeing linked by an epoxy bridge between respective positions in saidradicals ortho to the positions of said bonds, the remaining carbon atomwith two hydrogen atoms in each of said heterocyclic rings beingoxo-substituted, and each of said four p-aminop-henyl radicals having atleast one N-substituent selected individually from the group consistingof (i) an alkyl radical selected from the group consisting of methyl,ethyl, propyl, and butyl radicals, (ii) benzyl, (iii) methylbenzyl, (iv)phenyl, (v) naphthyl, (vi) chloromethyl, (vii) beta-hydroxyethyl, (viii)gamma-hydroxypropyl, (ix) delta-hydroxybutyl, (x) sulfophenyl, and (xi)tolyl.

7. A compound based on the structural formula tuted.

References Cited UNITED STATES PATENTS 2,449,088 9/1948 Smith 2603962,554,543 5/1951 Steiger 260-396 2,870,040 1/1959 Gill 117-362 2,935,9385/1960 OSullivan 101-1494 2,940,983 6/ 1960 Sartori 260346.2 3,012,04212/1961 Hoi 260346.2

WALTER A. MODANCE, Primary Examiner.

M. KATZ, Examiner.

J. A. PATTEN, Assistant Examiner.

1. A CHROMOGENOUS COMPOUND SELECTED FORM THE GROUP CONSISTING OF (A) A TETRAARYL-SUBSTITUTED COMPOUND BASED ON THE STRUCTURAL FORMULA